The invention relates to a circuit board and in particular to a printed circuit board (PCB) for a multi-package module for thermal dissipation and an electronic device using the same.
Demand for small, high performance portable electronic products such as mobile phones, protable computers, and the like have driven the industry to increase integration on semiconductor dice. Accordingly, the industry is achieving high integration by turning to 3D packaging by combining assembly technologies including wire bonding or flip chip to stack die packages to form a multi-package module (MPM).
MPM, a current assembly technology, integrates different dice functions, such as microprocessors or memory, logic, optic ICs, instead of placing individual packages onto a large printed circuit board (PCB). MPM, however, has a much higher power density than an individual single die package. Thus, thermal management is a key factor in its successful development.
FIG. 1 illustrates a conventional electronic device 100 with an MPM. The electronic device 100 comprises an MPM 20 mounted on a PCB 101, comprising a package substrate 12. The upper and lower surfaces of the package substrate 12 have dice 16 and 14 with different functions thereon, respectively, to create the MPM 20. For example, the die 16 is mounted on the upper surface of the package substrate 12 by bumps (or solder balls) of a package substrate 12′. The die 14 is mounted on the lower surface of the package substrate 12 by flip chip. The lower surface of the package substrate 12 comprises a plurality of bumps 10 thereon to correspondingly connect to the bonding pads (not shown) on the PCB 101. In the MPM 20, heat generated from the die 16 can be dissipated by radiation and convection. The gap g between the die 14 and the PCB 101 is too narrow, however, to dissipate the generated heat by radiation and convection. Accordingly, the heat generated from the die 14 is dissipated by conduction only. Typically, a metal layer 102 is disposed on the PCB 101 corresponding to the die 14 and connected to the die 14 by a heat conductive paste 22. That is, thermal dissipation is accomplished by a thermal conductive path created by the heat conductive paste 22, the metal layer 102 and the PCB 101.
Passive cooling, however, cannot provide a higher rate of adequate thermal dissipation for high power dice which may generate higher heat. That is, generated heat cannot be rapidly dissipated from dice by conducting the heat to the PCB through the heat conductive paste and the metal layer.